1. Field of the Invention
The present invention relates to heat exchangers, and more particularly to heat exchangers having first and second spiral tube arrangements conducting first and second heat exchange mediums, respectively, with a third heat exchange medium conducted through a plurality of ducts formed between, and surrounding, the tube spirals.
2. Description of the Prior Art
Many fields of use exist for tertiary heat exchangers: radiator exchangers, hot water exchangers in a heat pump, district heating systems or boiler stations, heat exchangers in water storage tanks, ground heat exchangers, etc.
Typically heating stations with heat pumps and/or district heating constitute an area where tertiary heat exchangers are required. In such stations, there is a flow of heat exchange medium into a first side of the exchanger, which is supplied with heat from a heat pump, a solar absorbator, or the like. A second side of the exchanger includes, on the one hand, a charging circuit of a storage tank for warm water, and on the other hand, a radiator circuit. Previously known heat exchangers of the tertiary type used in this field comprised separate stacks of tube spirals, each one conducting a heat exchange medium and positioned in a tank. Between the two stacks of tube spirals, a third heat exchange medium served as a heat exchanging agent.
A primary purpose of the invention is to provide a heat exchanger in which the effective lengths of flow of the two heat exchange mediums in the primary and secondary circuits can be made different, so that it is possible to optimize the quantity of exchanged heat at certain pressure drops and temperature levels. In practice, this can be attained in such a way that the media are conducted in spiral tubes and ducts from the center of the vessel to the periphery, or between an input position and an output position a bit from the center end the periphery. The effective length of the spiral duct can thereby be more or less shortened independent of the routes of flow of the other fluids, and can be located arbitrarily along the routes of these ones.